Backing wire for rotary drum filters



1 June 2, 1970 H. cs. VORE E T"AL 3,515,281

BACKING WIRE FOR ROTARY DRUM FILTERS 2 Sheets-Shet 1 Filed May 9, 1968INVENTORS HERBERT 6. VORE DONALD E. BARDSLEY.

ATTORNEY June 2, 1970 H. G. VORE ETAL 3,5

' BACKING WIRE on ROTARY DRUM FILTERS Filed May 1968- 2 Sheets-Shea:- 2

LLr

\ LLL INVENTORS HERBERT a. vow DONALD E. BARDSLEY ATTORNEY United StatesPatent 3,515,281 BACKING WIRE FOR ROTARY DRUM FILTERS Herbert G. Voreand Donald E. Bardsley, Nashua, N.H., assignors to Improved MachineryInc., Nashua, N.H., a corporation of Delaware Filed May 9, 1968, Ser.No. 727,921 Int. Cl. B01d 39/10 US. Cl. 210-402 7 Claims ABSTRACT OF THEDISCLOSURE A rotary drum filter including a drum having a plurality ofparallel, outwardly extending ribs each having a plurality of notchestherein. A filter screen supporting wire is helically wound around thedrum within the notches. The supporting wire is formed to cooperate withthe notches to thereby limit the movement of the wire of the drum due tostresses developed in the wire by variations in temperature. This may beaccomplished by forming a V in the wire or by twisting the wire.Apparatus is provided for forming the wire.

BACKGROUND OF THE INVENTION This invention relates to rotary drumfilters and more particularly to means for preventing the backing wireof a rotary drum filter from moving and stretching and accumulating atone end of the filter or backing wire section.

Rotary drum filters as used in the paper and pulp industry include adrum which rotates in a bath of material to be filtered. The drumnormally includes a cylindrical base having a plurality of parallel,outwardly projecting ribs extending along the length of the drum whichform filtrate flow guide means. Each support rib has a plurality ofspaced apart notches. A continuous wire is helically wound around thedrum within the notches. A single wire may be wound around the entiredrum, but it is usually preferable to wind the wire in approximatelytwo-foot sections measured along the length of the drum. A separate wireis used for each section. This wire is used to support a filteringelement such as a screen. As the drum rotates in the bath, liquid isfiltered through the screen into the channels formed by the ribs. Thesolid material or cake which is formed on the screen is then taken 01fby suitable rollers or other take-off devices well known in the art.

The wire is subjected to differences in temperature when the drum isrotated in the bath due to temperature differences between the vat,showers, take-off rolls and the like. These temperature differences setup stresses in the wire causing the wire to stretch and move relative tothe drum. The excess wire which results from the temperature differencestends to accumulate at one end of the wire section or, if a single wireis wound around the entire drum, at the end of the drum. This excesswire damages the filter screen, take-off rolls and other parts of themachine eventually causing failure of the machine.

Prior to this invention, attempts to solve the problem of wireaccumulation included placing the wire under high tension as it waswound around the drum. With modern machines which are used in moresevere conditions, the increased tension on the wire was found to beinadequate to overcome the problem. Another method of overcoming theproblem is shown in US. Patent No. 2,300,166, issued to J. B. Nowak. Inthat patent, a turn buckle is used to take up the slack in the wire asit stretches. Such an arrangement does not, however, prevent thestretching which, by the time it is discovered, can damage the machine.In addition, the slack which can be taken up by the turn buckle isinherently limited.

Although the problem can be substantially reduced by 'ice the use ofindividual wire sections which cover only a portion of the circumferenceof the drum, such as those shown in US. Patent No. 2,472,558, themanufacturing advantages of a continuous wire are lost. In addition, theindividual sections can stretch and cause damage to the machine. I

SUMMARY It is therefore the principal object of this invention toprovide an arrangement which prevents the backing wire of a rotary drumfilter from moving relative to the drum and accumulating at the end ofthe drum or wire section.

It is a further object of this invention to provide an arrangement whichprevents accumulation of the filter screen backing wire at the end ofthe wire sections of a rotary drum filter but does not requirealterations in the basic apparatus or method of manufacture.

In general, these and other objects are carried out by providing arotary drum filter comprising: a drum, a plurality of parallel,outwardly projecting ribs mounted on the outer periphery of said drum,each having a plurality of spaced apart notches in its outer edge; awire helically wound around said drum within said notches; said wirehaving at least one portion formed to cooperate with at least one ofsaid notches for retaining said wire tightly wound around said drum; andfilter means surrounding the outside of said drum and supported by saidwire.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be described inconnection with the annexed drawings wherein:

FIG. 1 is a perspective view of a rotary drum filter embodying thepresent invention;

FIG. 2 is a fragmentary view of a portion of a drum showing a firstembodiment of this invention partially applied to the drum;

FIG. 3 is a fragmentary view of a portion of a drum showing a secondembodiment of this invention;

FIG. 4 is a plan view of apparatus for forming the backing wire inaccordance with the first embodiment of this invention;

FIG. 5 is a fragmentary view of a portion of FIG. 4 with the apparatusin an advanced stage of forming the wire;

FIG. 6 is a perspective view of apparatus for forming the backing wirein accordance with the second embodiment of this invention;

FIG. 7 is a fragmentary view of a portion of a drum showing amodification of the second embodiment of this invention; and

FIGS. 8 and 9 are fragmentary views of portions of a dilferent type offilter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates asubstantially conventional rotary drum filter as used in the paper andpulp industry. Numeral 1 designates a bath which may be any conventionalarrangement used to contain material to be filtered. The drum 5 isrotatably mounted in the path 1. A plurality of parallel, outwardlyprojecting ribs 6 are mounted on the drum so that they are parallel tothe longitudinal axis of the drum. Each of the ribs 6 is provided with aplurality of notches 7 throughout its entire length. A beaking wire 8 ishelically wound around the drum within the notches -8. The wire 8 may bea continuous piece extending the entire lenght of the drum but,preferably, the drum is wound in sections so that if a wire fails, onlythat section in which the failure occurs need be replaced. Aconventional filter screen 9 covers the drum and is supported by thebacking wire 8.

The drum is rotated in the bath by a suitable motor means (not shown).As is more fully explained in US Pat. No. 3,363,774, during rotation ofthe drum, a vacuum is selectively applied to channels 15 formed by theribs 6 during portions of the rotary path of the drum. The vacuum drawsliquid through the filter screen 9 and a cake is formed on the screen.Conventional showers 11 are provided and a cake take-off roll 12 removesthe filtered material from the filter screen 9. An outlet 13 allows thefiltrate to be removed from the channels 15. The operation of the filterand the apparatus for applying a vacuum to the channels 15 areconventional and form no part of this invention.

The temperatures encountered during operation of the filter aredifferent from the temperatures encountered during the winding of thewire around the drum and there are temperature variations during thevarious phases of the operation of the filter. The differingtemperatures cause the wire 8 to stretch and move through the notches 7and accumulate at one end of the wire section. Such accumulation damagesthe screen 9 and take-off roll 12 eventually causing failure of themachine.

In order to substantially reduce this movement, the Wire 8 is formed tocooperate with the notches 7 to thereby retain the wire tightly woundaround the drum. In the embodiment of FIGS. 1 and 2 this function iscarried out by forming a V or zig zag in each wind of the wire 8. InFIG. 3 this function is carried out by twisting the wire betweenadjacent ribs or, as shown in FIG. 7, by twisting the wire at least 180and placing the center of the twist in a notch.

Referring to FIGS. 1 and 2 a V shape 18 (FIG. 2) is formed in each turnof the wire around the drum. This is done by removing the wire 8 from anotch 7 and placing it in a next higher notch 7. In carrying out theembodiment of FIGS. 1 and 2, the wire is wound completely around thedrum in the usual manner. The first notch 7 at the end of one rib 6 iseither widened so that it may accommodate two wires or an additionalnotch is provided. One portion of the second turn of the wire is thenmoved to the widened notch to form a V in the turn of the wire. The apex19 of the V is positioned in the notch, and the legs of the V terminatein a notch in the adjacent ribs. A portion of the third turn of the wireis then moved to the second notch to thereby form a. V in that turn. Atone point in each turn of the wire, the wire is displaced one notchuntil each turn of the wire has a V shape in it. This sequence isgenerally shown in FIG. 2.

In order to form the V-lock, a suitable tool shown in FIGS. 4 and hasbeen provided. This tool includes a frame 20 on which is mounted asupport 21. A toggle arrangement 22 having a handle 23 and bunter 24which may have a groove 25 therein are also mounted on the frame 20. Thesupports 21 carry a pair of stops 26 and 27 and cam follower rolls 28.In use, levers 31 are used to lift a portion of the wire 8 out of itsnormal notch 7. The toggle is moved forward or upward so that the wire 8is positioned in the groove 25 in the bunter 24. Continued forwardmovement of the toggle arrangement forms with the cam rollers a suitableV 18 in the wire 8. The apex 19 of the V is then fit within a notch 7which is aligned with the notches of the next wire turn while the legsextend down to the adjacent ribs as clearly shown in FIGS. 2 and 5. TheV forming tool is suitable for all sizes of filters in that it isadjustable by means of an adjusting slide 30 and adjusting bolts 29. Asthe size of the grid spacing is increased, the supports 21 may be movedapart. The stops 26 and 27 assure accurate alignment.

The spacing between the ribs 6 and the distance between the notches 7determine the holding power of the lock. As the spacing between the ribs6 is decreased and the distance between the notches is increased, theholding power of the lock will be increased. The amount of holding powerrequired is determined by the size and use of the filtering apparatus.On one unit having a one-inch spacing between ribs using a inch spacedD-shaped wire at 45,000 p.s.i. tension, the V-lock provided a holdingpower of 900 pounds against differential stresses. Each holding powerwas not heertofore obtainable by merely increasing the tension on theends of the wire. If greater holding power is desired, more than oneV-lock may be used in each turn of the wire.

A second embodiment of this invention is shown in FIG. 3. In thisembodiment rather than forming a V-lock in each turn of the wire, thearea between two adjacent ribs 6 is twisted as at 38 about its own axis.The twist not only tends to shorten the wire thereby increasing tension,but also prevents movement of the 'Wire in the notches. Since the wireis twisted, it cannot move through a notch 7. Each twist is preferablyat least but may be more. The twist for each turn of the wire around thedrum is preferably staggered from the twists of the adjacent turns. Ifgreater holding power is desired, more than one twist may be placed ineach turn.

A modification of the twist lock is shown in FIG. 7. In thismodification, a twist 48 of or a multiple thereof is formed in the wireand the center of the twist is placed in a notch 7. This modification isparticularly useful on filters where there is wide spacing between ribs.

In order to form the twists in the wire 8, a suitable tool shown in FIG.6 has been provided. This tool includes a jig plate 39 having a handle40 attached thereto. A pair of wire supports 41 extend outwardly fromthe jig plate 39, each having a groove 42 therein to support the wire 8.The wire supports 41 are connected to the plate 39 through adjustingholes 43. In order to apply the twist to the wire 8, a handle 44 havinga groove 45 is provided. The wire 8 is placed in the groove 45 and thehandle rotated as shown by the arrow in FIG. 6. To apply a 90 twist tothe wire, the handle 44 is rotated once to the position shown by brokenlines. If a twist of more than 90 is desired, the turning operation isrepeated until the desired angle is achieved. The jig is then removedand the wire 8 replaced in the notch 7 of the rib 6.

It has been found that the locking means of this invention isparticularly well suited for use on center valve louvered filters suchas that shown in U.S. Pat. No. 3,306,460 issued to O. Luthi. Theapplication of this invention to such a filter can be seen by referringto FIGS. 8 and 9 wherein filtrate flow guide means is generallydesignated at 50. In a louvered filter, the filtrate flow guide meansincludes supporting members 51 and cover element 52 which has anupwardly turned end 55 which forms a wire supporting rib having notchestherein. If the V-lock is to be used, three ribs 54 are added to theflow guide means 50 between adjacent cover elements 52. Each of theseribs is provided with a plurality of notches and the V-lock is formed atthese ribs in the same manner as with the filter shown in FIG. 1. If thetwist lock is to be used, it is not necessary to add the additionalribs. With the twist lock, a twist such as that shown in FIG. 7 may beformed in the wire and the center of the twist may be placed in a notchin the upturned end or rib 55. The twist on opposite sides of the ribprevent movement of the wire through the notch.

In both the V-lock and the twist lock, the cooperation between theformed wire and the notches 7 and ribs 6 holds the wire tightly againstthe ribs 6 within the notches 7. The stretching due to the increases intemperatures is limited to a single turn of the wire around the drum 5.The twist or V-lock retains the wire tightly wound around the drumwithin the notches and prevents the wire from accumulating at one end ofa wire section or the drum. Longer life of the screen 9 and filterapparatus as a whole is thereby provided.

From the foregoing it is apparent that the objects of this inventionhave been carried out.

We claim:

1. A rotary drum filter comprising:

a drum;

a plurality of parallel, outwardly projecting ribs mounted on the outerperiphery of said drum, each having a plurality of spaced apart notchesin its outer edge;

a wire helically wound around said drum within said notches to therebyform a plurality of turns;

means cooperating with said notches for anchoring said wire within saidnotches at a plurality of locations between the ends of said drum forretaining said wire tightly wound around said drum; and

filter means surrounding the outside of said drum and supported by saidwire;

in a plurality of turns of said wire around said drum, said wire beingtwisted between two adjacent ribs to cooperate with said notches to formsaid means for anchoring said wire within said notches.

2. The rotary drum filter of claim 1 wherein the twists for successiveturns of said wire are staggered.

3. A filtering apparatus comprising:

a drum;

filtrate flow guide means mounted on the outer periphcry of said drumand including a plurality of outwardly projecting ribs each having aplurality of notches in its outer edge;

a wire substantially continuously helically wound around said drumwithin said notches to form a plurality of turns;

means positioned at a plurality of locations between the ends of saiddrum for anchoring said wire within said notches for retaining said wiretightly wound around said drum; and

filter screen means surrounding said drum and supported by said wire;

each turn of said wire around said drum having at least one portionwhich is twisted at least 180 and the center of the twist is placed inone of said notches to cooperate with said filtrate flow guide means toform said means for anchoring said wire within said notches.

4. A filtering apparatus comprising:

a drum;

filtrate flow guide means mounted on the outer periphery of said drumand including a plurality of outwardly projecting ribs each having aplurality of notches in its outer edge;

a wire substantially continuously helically wound around said drumwithin said notches to form a plurality of turns;

means positioned at a plurality of locations between the ends of saiddrum for anchoring said wire within said notches for retaining said wiretightly wound around said drum; and

filter screen means surrounding said drum and supported by said wire;

each turn of said wire around said drum having a V formed therein andthe apex of said V being positioned in one of said notches to cooperatewith said filtrate flow guide means to form said means for anchoringsaid wire within said notches.

5. A rotary drum filter comprising:

a drum;

a plurality of parallel, outwardly projecting ribs mounted on the outerperiphery of said drum, each having a plurality of spaced apart notchesin its outer edge;

a wire helically wound around said drum within said notches to therebyform a plurality of turns;

means cooperating with said notches for anchoring said wire within saidnotches at a plurality of locations between the ends of said drum forretaining said wire tightly wound around said drum; and

filter means surrounding the outside of said drum and supported by saidwire;

in at least some of said turns of said wire around said drum, said wirebeing twisted at least 180 about its own axis and the center of thetwist is positioned in a notch of one of said ribs to form said meansfor anchoring said wire within said notches.

6. A rotary drum filter comprising:

a drum;

a plurality of parallel, outwardly projecting ribs mounted on the outerperiphery of said drum, each having a plurality of spaced apart notchesin its outer edge;

the notches of each rib being substantially parallel to the notches ofthe adjacent ribs;

a wire helically wound around said drum within said notches to therebyform a plurality of turns;

means cooperating with said notches for anchoring said wire within saidnotches at a plurality of locations between the ends of said drum forretaining said wire tightly wound around said drum; and

filter means surrounding the outside of said drum and supported by saidwire;

at least some of the turns of wire around said drum having a V formedtherein and the apex of said V is positioned in one of said notches toform said means for anchoring said wire within said notches.

7. The rotary drum filter of claim 6 wherein the apex of said V ispositioned in a notch in a first rib and the legs of said V terminate ina notch in the ribs adjacent said first rib.

References Cited UNITED STATES PATENTS 21,7 68 10/1868 McMurry 162-357548,263 10/1895 Morgan -l02 X 799,153 9/1905 Mullner 210401 X 1,020,0733/1912 Bell.

1,327,962 1/ 1920 Petti 210-402 1,911,310 5/1933 Ellis 162--3572,145,933 2/ 1939 Kehrer -i .210-402 2,165,456 7/1939 Cox 140932,472,558 6/1949 Ackerly 210-402 X REUBEN FRIEDMAN, Primary Examiner T.A. GRANGER, Assistant Examiner

